Combustion chamber for a gas turbine plant

ABSTRACT

A combustion chamber (1) for a gas turbine plant having a combustion chamber wall (10), through which combustion gases (G) flow in the direction of a downstream gas turbine, wherein the combustion chamber wall (10) has a dampening device (20) for dampening thermoacoustic vibrations caused by the combustion gases (G) and wherein the dampening device (20) comprises at least one Helmholtz resonator. The resonator volume (21) opens into the combustion chamber (1) with the resonator tube opening (M) in the combustion chamber. At least one supply opening (23) with which sealing air (S) for sealing the resonator tube opening (M) is introduced into the combustion chamber (1) via the resonator volume (21) and an at least one resonator tube (22, 22′, 22″) from a compressor plenum (2). The at least one resonator tube (22, 22′, 22″) from a compressor plenum (2). The at least one resonator tube (22′, 22″) has a tube axis (A) in the combustion chamber wall and the axis (A) lies outside of a surface normal (N) of the combustion chamber wall (10) at the site of the resonator tube opening (M).

The invention relates to a combustion chamber for a gas turbine plant according to the preamble of claim 1 and to a correspondingly designed gas turbine plant according to claim 6.

Gas turbine plants are composed essentially of a compressor, of a combustion chamber with a burner and of an expansion turbine. In the compressor, sucked-in air is compressed before it is mixed with fuel in the combustion chamber in the following burner arranged in the compressor plenum, and this mixture is burnt. The expansion turbine following the combustion chamber then extracts thermal energy from the combustion exhaust gases which have occurred in the burner and converts this into mechanical energy. A generator capable of being coupled to the expansion turbine can convert this mechanical energy into electrical energy for current generation.

Nowadays, gas turbine plants, like other current-generating plants, too, must have, when working at maximum efficiency, pollutant emissions which are as low as possible in all load ranges. Major influencing variables are in this case the mass flow rates, set in the combustion chamber of the burner, of the fuel, of the compressed air and of the cooling air delivered for cooling the burner components. However, the limitation of pollutant emissions, in particular of NOx and unburnt fuel mostly in the form of CO, may in this case lead to a minimization of the quantity of cooling air or of leakage air in the combustion chamber and consequently to parasitic flows which have an acoustically damping effect. Furthermore, under the boundary condition of limiting the emissions, an increase in efficiency also usually entails an increase in the volumetric heat release density in the combustion chamber. The two together, that is to say a reduction in acoustic damping and an increase in the heat release density in the combustion chamber, lead to a higher risk that thermoacoustically induced vibrations commence.

However, thermoacoustic vibrations of this kind in the combustion chamber present a problem in the design and, in particular, in the operation of gas turbine plants.

To reduce such thermoacoustic vibrations, Helmholtz resonators, which are composed of at least one resonator tube and of a resonator volume, are employed nowadays for damping. Helmholtz resonators of this kind damp the amplitude of vibrations at the Helmholtz frequency in specific frequency ranges as a function of the cross-sectional area and the length of the resonator tube and of the resonator volume. Helmholtz resonators as damping devices for limiting thermoacoustic vibrations in combustion chambers are known, for example, from EP 1 605 209 A1 or US 2007/0125089 A1.

FIG. 1 shows, for example, the arrangement, known from US 2007/0125089 A1, of Helmholtz resonators 20 on a ring of the combustion chamber wall 10 transverse to the flow direction. The combustion chamber wall 10 is in this case of tubular form and separates the combustion chamber 1 from the surrounding compressor plenum 2. The perforations 22 in the combustion chamber wall 10 between the resonator volume 21 and combustion chamber 1 form the resonator tubes of the Helmholtz resonators.

In this case, as illustrated in FIG. 1, each Helmholtz resonator may have a plurality of resonator tubes or else only a single resonator tube. So that none of the hot combustion gases from the combustion chamber 1 are introduced into the Helmholtz resonators 20, additional ports for the delivery of barrier air are provided. In the exemplary embodiment shown in FIG. 1, these delivery ports 23 are arranged on that wall of the resonator volume 21 which lies opposite the resonator tubes 22. These ports 23 make it possible that compressed air S can flow out of the compressor plenum 2 surrounding the combustion chamber into the resonator volume 21 and from there, via the resonator tubes 22, into the combustion chamber 1, thus barring the infiltration of hot combustion gases into the resonator tubes 22.

However, Helmholtz resonators with deliveries of barrier air via the volume body have the disadvantage that the barrier air flows via the resonator tubes into the combustion chamber and consequently influences the air/fuel mixture prevailing there. Precisely where known designs are concerned, in which the resonator tubes are arranged in the combustion chamber wall such that, on the location where the resonator tubes issue into the combustion chamber, the resonator tube axis comes to lie in the normal to the surface of the combustion chamber inner wall, barrier air is introduced with a maximum depth of penetration into the combustion space of the combustion chamber. However, this maximum cross current in relation to the internal flow of the combustion chamber may lead, precisely in the low load range of the gas turbine plant, to partial quenching of combustion and consequently to an increase in CO pollutant emission.

The object of the invention is to provide a combustion chamber which overcomes the disadvantages described above.

This object is achieved by means of the combustion chamber having the features of claim 1.

Since a combustion chamber, designed according to the preamble of claim 1, with at least one Helmholtz resonator has at least one resonator tube which is arranged such that, at the location of issue of the resonator tube into the combustion chamber, it lies with its resonator tube axis outside a normal to the surface of the combustion chamber inner wall, the maximum depth of penetration of the barrier air into the combustion space of the combustion chamber is reduced, the more so, the further the resonator tube axis is inclined in relation to the surface normal. Combustion in the combustion chamber is thereby influenced to a lesser extent, so that an increase in pollutant emission, in particular increased CO emission when the gas turbine plant is under part load, can be largely avoided.

At the same time, with an increasing inclination angle, a region with film cooling is formed increasingly on the combustion chamber inner wall by the injected barrier air. Since the air flowing in from the compressor plenum via the Helmholtz resonator is colder than the combustion gases in the combustion chamber, an improved capacity for cooling the combustion chamber wall can thus be achieved. At larger inclination angles, in particular at inclination angles of approximately 45 degrees or more, between the normal to the surface of the inside of the combustion chamber wall and the resonator tube axis in the downstream direction, a significant part of the barrier air flowing in via the resonator tube is entrained by the flow inside the combustion chamber and flows downstream along the combustion chamber inner wall, near the wall, so as to have a cooling effect over a larger region, before the barrier air is mixed more and more with the combustion gases and therefore assumes the same temperature as the combustion gases. Moreover, with an increasing inclination angle, the resonator tubes become increasingly longer, with the result that ever better convection cooling of the combustion chamber wall is achieved.

Further preferred exemplary embodiments may be gathered from the subclaims. What is essential in all the combustion chamber versions is that a zone for mixing the cooler barrier air with the hot mass flows is configured in the combustion chamber such that, particularly in the low load range, partial quenching of combustion by the cooler barrier air is suppressed, but without the damping properties of the Helmholtz resonators being influenced. Gas turbine plants equipped with such combustion chambers can thus have as low pollutant emissions as possible in all load ranges, while working at maximum efficiency.

The invention is in this case not restricted to the inclination of the resonator tubes being solely in the flow direction of the combustion exhaust gases. On the contrary, without any further restriction of the present invention, versions may also be envisaged in which the resonator tubes have in relation to the normal to the surface of the combustion chamber inner wall an inclination which is composed both of an inclination fraction in the flow direction and of an inclination fraction transversely thereto.

The resonator tubes can thus be adapted optimally to the local conditions of the internal flow of the combustion chamber.

The invention, then, may be explained by way of example by means of the following figures in which:

FIG. 1 shows diagrammatically a damping device known from the prior art,

FIG. 2 shows diagrammatically a first version according to the invention of a damping device,

FIG. 3 shows diagrammatically a second version according to the invention of a damping device.

The concept according to the invention for injecting barrier air S into the combustion space of the combustion chamber 1 of a gas turbine plant is described below, by way of example, by means of a burner which is based on a tubular combustion chamber and in which the damping device 20 is adapted essentially to the outside of the combustion chamber wall 10. However, the invention is also just as suitable for use in burners in which the damping device 20 is integrated completely in the combustion chamber wall 10, or else in any other version in which barrier air S is delivered via the damping device 20.

FIG. 2 illustrates a detail of a combustion chamber 1 along the flow direction of the combustion gases G, with a routing of barrier air in which, in contrast to the prior art, the barrier air S is routed into the combustion space 1 at an angle α larger than zero degrees (here approximately 45 degrees) in relation to the normal N to the surface of the combustion chamber inner wall of the combustion chamber 10. As a result, the depth of penetration of the barrier air S into the combustion chamber 1 can be reduced significantly, and moreover the zone of the mixing of the barrier air S with the combustion gases G is relieved axially. Consequently, that region of the combustion chamber internal flow which is intermixed with cooler barrier air is made smaller, thus leading, overall, to a marked reduction in pollutant emission. At the same time, by the flow being routed near the surface on the combustion chamber inner wall, a region B is formed, in which significant mixing between cooler barrier air S and the combustion gases G has not yet taken place, so that, in addition, the film cooling properties of the injected barrier air S can be improved, with the result that the thermal load upon the combustion chamber walls can be reduced.

Since, due to the oblique arrangement of the resonator tubes, the damping properties of the Helmholtz resonators may, with the resonator volume otherwise being the same and with the number of resonator tubes kept constant, deviate from those of the Helmholtz resonators known from the prior art and having perpendicular injection, it is usually necessary for the damping properties of the resonator parameters to be adapted. This may take place, for example, by a variation in the number of resonator tubes 22′ and/or the delivery ports 23 and/or their diameters or by a change in the resonator volume 21.

In the event that a combination with a plurality of Helmholtz resonators composed of resonators having different Helmholtz frequencies and therefore different damping properties is employed, it is recommended that subsets with Helmholtz resonators of a different type be formed. FIG. 3 illustrates the case where Helmholtz resonators of a different type are arranged in different axial positions of the combustion chamber. The variant illustrated here is aimed at injecting part of the barrier air S as far upstream as possible, that is to say in the direction of the heat release zone (resonator type 1), and at injecting part of the barrier air S as far downstream as possible (resonator type 2). For this purpose, the Helmholtz resonators of type 1 arranged on a first ring around the tubular combustion chamber have resonator tubes 22″, the axes A of which are inclined at an angle α in the upstream direction to the normal N to the surface of the combustion chamber inner wall, and the Helmholtz resonators of type 2 arranged in a second ring have resonator tubes 22′, the axes A of which are inclined at an angle α in the downstream direction to the surface normal N.

As a result, on the one hand, as near-wall a flow as possible for intensified film cooling B can be achieved by the ring having type 2 resonators and at the same time further superposed film cooling B′ can be achieved with the ring having type 1 resonators, and this can lead, overall, to a reduction in barrier air. However, the invention is in this case not restricted only to the embodiment illustrated in FIG. 2. On the contrary, it is also intended to embrace versions which are composed, for example, only of type 1 or type 2 resonators or else of resonator types with different inclination angles α. It may just as well be envisaged that a ring already has various resonator types over the circumference of the combustion chamber wall, in order thereby to achieve optimal adaptation to the local conditions of the internal flow of the combustion chamber. 

1. A burner with a combustion chamber for a gas turbine plant, the combustion chamber includes: a combustion chamber wall , through which combustion gases flow in a direction of a following gas turbine; the combustion chamber wall having a damping device for the damping of thermoacoustic vibrations caused by combustion gases, the damping device comprising at least one Helmholtz resonator which is configured such that a resonator volume thereof lies on a side of the combustion chamber wall that faces away from an inner side of the combustion chamber wall; the resonator has at least one resonator tube in the combustion chamber wall, the tube co-operates with internal volume of the resonator, and the resonator tube has a mouth lying opposite the resonator volume on the inner side of the combustion chamber wall and exits into the combustion chamber; at least one delivery port into the resonator configured for entry of barrier air in such manner as for barring the resonator tube mouth from a compressor plenum that surrounds the combustion chamber, wherein the barrier air is introduced into the combustion chamber via the resonator volume and then by the at least one resonator tube; and the at least one resonator tube has a resonator tube axis in the combustion chamber wall such that, at the location of a resonator tube mouth, which is into the combustion chamber, the resonator tube axis lies outside a normal to the surface of and oblique to the combustion chamber inner wall.
 2. The burner with a combustion chamber as claimed in claim 1, wherein the resonator tube axis of the resonator tube is inclined away from a surface of the inner wall normal, in an upstream direction or a downstream direction of the combustion gases flowing through the combustion chamber.
 3. The burner with a combustion chamber as claimed in claim 2, wherein there is flow in the combustion chamber past the inner wall thereof from the upstream to the downstream directions; the resonator tube axes of upstream inclined direction resonator tubes of the Helmholtz resonator are inclined in the upstream direction, and the resonator tube axes of downstream inclined direction resonator tubes of the Helmholtz resonator are inclined in the downstream direction.
 4. The burner with a combustion chamber as claimed in claim 1, wherein the damping device comprises a multiplicity of Helmholtz resonators which are arranged over a circumference of the combustion chamber wall, that the resonators are distributed on at least one ring transversely to the combustion gases flowing through.
 5. The burner with a combustion chamber as claimed in claim 4, wherein the upstream inclined resonator tubes are assigned to the Helmholtz resonators of a first ring thereof and the downstream inclined resonator tubes inclined downstream are assigned to the Helmholtz resonators of a second ring lying downstream.
 6. A gas turbine plant comprising: the burner of claim 1 for admixing of fuel and for combustion of the fuel/air mixture; a compressor for the compression of sucked-in air, a combustion chamber following the compressor and receiving the air after compression of the air; and an expansion turbine which follows the burner and which converts the combustion exhaust gases of the burnt fuel/air mixture into mechanical energy. 